Lithium greases containing naphthenyl diesters



United States Patent LITHIUM GREASES CONTAINING NAPHTHENYL DIESTERS Samuel E. Jolly, Ridley Park, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application May 20, 1955 Serial No. 510,020

4 Claims. (Cl. 252-42) This invention relates to lubricating greases, and more particularly to greases comprising a lithium soap dispersed in a modified synthetic lubricating base.

Lithium soap greases, particularly well adapted for low temperature operation, or for operation over a wide lubricating temperature range, have previously been compounded from lithium soaps of saturated fatty acids, preferably a hydroxy stearic acid, and synthetic lubricant bases such as branched chain liquid aliphatic esters of saturated dicarboXylic acids of from 4 to 12 carbon atoms. Esters particularly suited for such use as a lubricating base include esters of such acid-s as sebacic, glutaric, succinic, suberic, pimelic, azelaic, alkenyl-succinic, alkylmaleic, etc., the alcoholic component of which is preferably branched chain. Typical of greases of this type are those disclosed in U. S. Patent 2,450,222 to Ashburn et al.

While such synthetic lithium greases possess superior lubricating qualities, it has been found that unless their manufacture is very carefully controlled, they tend to become cloudy and grainy, and do not present the clear, buttery appearance which purchasers of greases demand. Even under the most carefully controlled manufacturing conditions, it is not always possible to compound greases which meet specifications as to appearance. Furthermore, their A. S. T. M. penetration tends to be somewhat high.

It is an object of this invention to provide synthetic lithium greases of clear and buttery appearance.

It is a further object of this invention to provide synthetic lithium greases of improved penetration characteristics.

I have found that the foregoing advantages may be obtained by replacing a part of the aliphatic ester lubricant base with a naphthenyl ester of a dibasic acid. The naphthenyl ester may be an ester of any of the acids mentioned above, and should be present in the mixed lubricant base in the amount of at least since if less than 10% is present there will not be a noticeable improvement in the properties of the grease. If more than about 50% of the aliphatic ester is replaced by the naphthenyl ester, the lubricant base may have a viscosity higher than desirable for most applications, but for certain special uses, such as for high temperature lubrication, the aliphatic ester may be replaced entirely by the naphthenyl ester.

In order to illustrate my invention more clearly and the advantageous results obtained thereby, the results of tests are given in the following table. The greases tested were made by combining 100 parts by weight of the lubricant base with 10 parts by Weight of a lithium hydroxystearate soap, heating the mixture to 400 F. to dissolve the soap in the lubricating base, and then cooling rapidly with agitation to room temperature.

2,824,065 Patented Fella. 18, 1958 The PleXol 201 used in the formulation was a commercial dioctyl sebacate supplied by Rohm and Haas, having the following physical characteristics:

Sap. No 263 Vis., SUS/ F 68.3 Vis., SUS/210 F 37.3 V. I Pour test F 65 The dinaphthenyl sebacate used in the formulation was made by esterifying sebacic acid with naphthenyl alcohol derived from naphthenic acids having an average molecular weight of about 330, and an average type formula of C H O The ester had the following physical characteristics.

Sap. No 112 Acid No 0.9 Hydroxyl No 14.8 Vis., SUS/l00 F 492.7 Vis., SUB/210 F 63.3 V. I 98 Pour test F -35 While in the examples given in the table the soap content of the grease was held constant, it should be apparent that the soap may be present in varying proportions, depending on the desired consistency of the grease. For example, if a soft grease is desired, the soap may be present in the amount of 5% or so, while if a hard grease is desired, the soap content may be increased to 20% or more. Similarly, while a lithium soap of hydroxystearic acid is preferred, the soap may be a mixture of lithium hydroxystcarate and lithium stearate, or lithium stearate alone, and soaps of other metals may be present.

The reason why the naphthenyl ester improves the quality of the grease is not fully understood, but it is believed that it may act as a mutual solvent for the soap and the aliphatic ester employed, and may also act as a crystallization inhibitor during the cooling of the grease, to prevent formation of grainy soap fibers. In any event, its effect seems to be tied in some way to the ring structure of the naphthenyl radical, and is not particularly dependent on the molecular weight, since esters made from naphthenyl alcohols of an average molecular weight of from about 200 to about 4-00 or more appear to function in about the same manner.

While the foregoing description does not mention the use of other additives well known to the grease-making art, such as anti-oxidants, anti-rust agents, and the like, it will be understood that such agents may be added to my greases in the customary amounts without departing from my invention, which should be construed as covering all synthetic base lithium greases containing, as part of the synthetic base, at least 10% of a naphthenyl diester of a dicarboxylic acid.

I claim:

1. A grease comprising a synthetic lubricant base composed of esters of dicarboxylic acids and comprising at least 10% of a naphthenyl diester of a dicarboxylic acid, and suflicient lithium soap of a soap-forming fatty material to thicken said lubricant base.

2. A grease comprising a synthetic lubricant base, consisting of from about 50% to about 90% of an aliphatic 5 diester of a dicarboxylic acid and from about 50% to 10% of a naphthenyl diester of a dicarboxylic acid, and suflicient lithium soap of a soap-forming fatty material to thicken said lubricant base. 2,448,567

3. The grease according to claim 2 in which the 10 2,450,222

sebacate.

naphthenyl diester of a dicarboxylic acid is dinaphthenyl 4-. The grease according to claim 3 in which the aliphatic diester of a dicarboxylic acid is dioctyl sebacate.

References Cited in the file of this patent UNITED STATES PATENTS Zisman et a1. Sept. 7, 1948 Ashburn et a1 Sept. 28, 1948 

1. A GREASE COMPRISING A SYNTHETIC LUBRICANT BASE COMPOSED OF ESTERS OF DICARBOXYLIC ACIDS AND COMPRISING AT LEAST 10% OF A NAPHTHENYL DIESTER OF A DICARBOXYLIC ACID, AND SUFFICIENT LITHIUM SOAP OF A SOAP-FORMING FATTY MATERIAL TO THICKEN SAID LUBRICANT BASE. 